[Show abstract][Hide abstract] ABSTRACT: In this paper, we introduce a simple and effective method to improve the transmission power respond of a polyelectrolyte (PE)-coated arc-induced long-period fiber grating (LPFG) sensor toward external perturbation. Experiments using single-pass and double-pass configurations were conducted to measure sucrose concentrations of between 0 and 80 wt%. The results showed that the transmission power sensitivity of the PE-coated LPFG sensor in the double-pass configuration was almost double compared to the single-pass configuration.
Journal of Electromagnetic Waves and Applications 07/2015; DOI:10.1080/09205071.2015.1066715 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A simple and rapid pre-concentration technique was proposed for the simultaneous determination of eight trace heavy metals in water by energy-dispersive X-ray fluorescence (EDXRF) spectrometry. Yttrium was added as a carrier ion to a sample solution containing Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The metals were collected on a membrane filter as precipitates or co-precipitates with 1-(2-pyridylazo)-2-naphthol at pH 10. The metals on the filter were determined by EDXRF spectrometry. Yttrium improved the collection efficiency of Cr(III) drastically and also expanded the pH ranges for quantitative recoveries of the metals. Only fifteen min was required to prepare the membrane filter retaining the metals. Linear calibrations were obtained from μg L-1 to mg L-1 levels of the metals in 50 mL sample solution. The limits of detection were as follows: Cd, 1 μg L-1 ; Cr, 0.3 μg L-1; Cu, 1 μg L-1; Fe, 1 μg L-1; Mn, 0.3 μg L-1; Ni, 2 μg L-1; Pb, 2 μg L-1; Zn, 2 μg L-1. The sensitivities were enough for monitoring drinking water. The proposed method was applied to river water and underground waters. The analytical results were agreed with those obtained by GF-AAS for the detected metals. The recoveries of the spiked metals in the waters were quantitative. This method was advanced to the separation and determination of Cr(III) and Cr (VI). The proposed system of pre-concentration and EDXRF spectrometry has high potential for routine monitoring of trace heavy metals because of its simplicity and rapidity besides cost-effectiveness.
[Show abstract][Hide abstract] ABSTRACT: A study based on the physicochemical parameters and dissolved metals levels from three main rivers around Dhaka City, Bangladesh, was conducted in order to determine the present pollution status and their alteration trends with the seasonal change of discharge amount. The water samples were collected from the rivers Buriganga, Turag, and Shitalakkhya during both dry and monsoon seasons. Physicochemical analyses revealed that most of the water quality parameters exceeded the recommended levels set by the Department of Environment (DoE), Bangladesh, during both the dry and monsoon OPEN ACCESS Environments2015, 2 281 seasons. A very strong positive correlation was found between biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in all sampling points. Both BOD and COD values had a strong negative correlation with dissolved oxygen (DO) in the Shitalakkhya River. Most of the dissolved metals concentrations in the water samples were similar. However, the concentrations of different physicochemical properties varied with the seasons. The dry season had significantly higher contamination loads, which were decreased during the monsoon season. Anthropogenic activities, as well as the variation in river water flow during different seasons were the main reasons for this high degree of water pollution.
[Show abstract][Hide abstract] ABSTRACT: A rapid and simple method for the determination of anionic surfactants based on an evanescent wave fiber optic was developed using ethyl violet. The sensor was prepared by removing the middle of the multimode fiber cladding. The optical signal from ethyl violet decreased with an increase in the sodium dodecyl sulfate concentration. The calibration curve was linear from 4 to 15 milligrams per liter with a limit of detection of 3.3 milligrams per liter. This simple fiber optic sensor requires a low volume of sample and does not employ extraction with organic solvents compared with conventional methods.
[Show abstract][Hide abstract] ABSTRACT: Soil enzymes play essential roles in catalyzing reactions necessary for nutrient cycling in the biosphere. They are also sensitive indicators of ecosystem stress, therefore their evaluation is very important in assessing soil health and quality. The standard soil enzyme assay method based on spectroscopic detection is a complicated operation that requires the removal of soil particles. The purpose of this study was to develop a new soil enzyme assay based on hydrodynamic electrochemical detection using a rotating disk electrode in a microliter droplet. The activities of enzymes were determined by measuring the electrochemical oxidation of p-aminophenol (PAP), following the enzymatic conversion of substrate-conjugated PAP. The calibration curves of β-galactosidase (β-gal), β-glucosidase (β-glu) and acid phosphatase (AcP) showed good linear correlation after being spiked in soils using chronoamperometry. We also performed electrochemical detection using real soils. Hydrodynamic chronoamperometry can be used to assess the AcP in soils, with a detection time of only 90 s. Linear sweep voltammetry was used to measure the amount of PAP released from β-gal and β-glu by enzymatic reaction after 60 min. For the assessment of soil enzymes, the results of hydrodynamic voltammetry assay compared favorably to those using a standard assay procedure, but this new procedure is more user-friendly, rapid and simple.
[Show abstract][Hide abstract] ABSTRACT: This study proposes an optical fiber sensor for calcium carbonate (CaCO3) scale formation in water. The sensor is easily fabricated by removing the cladding of a multimode fiber to expose the core towards the surrounding medium in order to detect refractive index change. A variation of the transmittance response from the high refractive index of CaCO3 which precipitated on the fiber core surface was observed. The proposed setup can be used to analyze the transmittance response over wide range of wavelength using white light as a source and also a spectroscopy detector. The curve of the transmittance percentage over time showed that a fiber core with 200 μm has higher sensitivity as compared to a fiber core with 400 μm. The findings from this study showed that the sensor detection region at near infrared (NIR) wavelengths showed better sensitivity than visible light (VIS) wavelengths. Field tests were conducted using natural geothermal water at Matsushiro, Japan in order to verify the performance of the proposed sensor. The optical response was successfully evaluated and the analytical results confirmed the capability of monitoring scale formation in a geothermal water environment.
[Show abstract][Hide abstract] ABSTRACT: A sensitive visual colorimetry was proposed for the on-site determination of arsenic in drinking water supplied from ground water. The method was based on an advanced molybdenum blue (MB) colorimetry combined with enrichment technique using membrane filter. A portable device equipped with two attachments of a CaCO3-cartridge was used to eliminate interference from phosphate and a tiny membrane holder to retain the MB was proposed for on-site analysis. Ten mL of sample solution containing 0.1-0.4 μg arsenic was passed through the CaCO3-cartridge. The arsenic in the sample solution was converted into MB and collected on a membrane filter as an ion-associate with a cationic surfactant. The arsenic was determined visually from the color intensity of the filter using color chart made from standard solution. The sensitivity is sufficient to detect the concentration of 10 μg L-1 adopted by the WHO standard. The speciation analysis for As(III) and As(V) was also successfully performed. The proposed method was applied to several ground water samples, and the analytical results were well comparable with those obtained by HG-AAS.
[Show abstract][Hide abstract] ABSTRACT: In this study, a peptide-1 (RNRCKGTDVQAW) constructing lysozyme was conjugated with an electroactive daunomycin in order to voltammetrically detect ovalbumin (OVA). Hetero-bifunctional cross-linking agents with four kinds of ethylene chains in differing lengths were used to bind the peptide-1 and daunomycin. After a cross-linking agent had reacted with an amino group of daunomycin, the compound was introduced into the peptide to the cysteine residue in the peptide using a pendant arm. The OVA was sensed via a change in the electrode response of the daunomycin moiety, based on the binding between the peptide and the OVA. The adsorption of the peptide probe on the electrode increased with increases in the ethylene chain. The binding constants between the peptide probes and the OVA, however, did not depend on the length of the chain. This was because the ethylene chain influenced the binding. When the peptide and the daunomycin were bound using N-(6-maleimidocaproyloxy) sulfosuccinimide, the electrode response of the peptide probe was the most sensitive from among the four cross-linking agents. The calibration curve of the OVA using the peptide probe was linear and ranged from 1.5 × 10−11 to 3.0 × 10−10 M. Furthermore, this method could be applied to the electrochemical sensing of the OVA in egg whites and in fetal bovine serum.
[Show abstract][Hide abstract] ABSTRACT: Herein, we present a novel spectroelectrochemical fiber optic sensor that combines electrochemistry, spectroscopy, and electrostatic adsorption in three modes of selectivity. The proposed sensor is simple and consists of a gold mesh cover on a multimode fiber optic that uses attenuated total reflection (ATR) as the optical detection mode. The sensing is based on changes in the attenuation of the light that passes through the fiber optic core accompanying the electrochemical oxidation-reduction of an analyte at the electrode. Methylene blue and ferrocyanide were used as model analytes to evaluate the performance of the proposed sensor. The optical transmission changes generated by electrochemical manipulation showed a good linear relationship with the concentration and the limits of detection (3σ) for methylene blue and ferrocyanide at 2.0×10-7 M and 1.6×10-3 M, respectively. The sensor responses were successfully enhanced with an additional level of selectivity via an electrostatically adsorpted, self-assembled monolayer (SAM), which consisted of a silane coupling layer, a poly anion, and a poly cation. The improvement observed in the sensitivity of a SAM-modified fiber optic sensor was rather encouraging. The optimized sensor had detection limits (3σ) for 8.3×10-9 M of methylene blue and 7.1×10-4 M of ferrocyanide. The developed sensor was successfully applied to the detection of ferrocyanide in stimulated nuclear waste.
[Show abstract][Hide abstract] ABSTRACT: Tetrabromobisphenol A (TBBPA), a type of brominated flame retardant that shows endocrine disruption effects, has been identified in leachates from landfills. Iron(III)-porphyrins that mimic the active site of peroxidases have been shown to be effective in oxidizing halogenated phenols, such as TBBPA. In the present study, TBBPA was subjected to oxidation with potassium monopersulfate (KHSO5) using an iron(III)-phthalocyanine-tetrasulfonic acid (FePcTS), structural analogue of iron(III)-porphyrin, in the presence of humic acid (HA), a major component in landfill leachates. When TBBPA was oxidized using the above system, the levels of degradation and debromination increased with increasing pH in the presence of HA. Because of landfill leachates are weakly alkaline (around pH 8), oxidation products derived from TBBPA were investigated at pH 8. Approximately 48% of the bromine in the degraded TBBPA was incorporated into HA, and hydroxy-tribromobisphenol A was determined to be the major brominated intermediate in the HA fraction. In the iron(III)-porphyrin catalytic systems, the brominated intermediate incorporated into HA is mainly TBBPA, and no hydroxy-substituted bromophenols are found. Thus, the catalytic power of FePcTS is higher than that of iron(III)-porphyrin catalysts.
Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 07/2014; 49(9):981-7. DOI:10.1080/10934529.2014.894810 · 1.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For this study, a new method was developed to electrochemically detect ovalbumin via its binding with the peptide-1(RNRCKGTDVQAW) in lysozymes. The peptide that exists at the C-terminal of a lysozyme was combined with ovalbumin. When an electroactive compound was introduced to the N-terminal side of the peptide through ethylene gycolbis(sulfosuccinimidyl succinate), the labeled peptide-1 served as a probe for the detection of ovalbumin. The electrode responses of labeled peptide-1 were measured after the labeled peptide-1 and ovalbumin were incubated in a 0.1M phosphate buffer (pH 5.6). As a result, the electrode response decreased as the concentration of ovalbumin increased. The detection limit of ovalbumin was 2.3×10(-11)M as estimated at 3-fold the standard deviation (3σ) (n=5). Because the steric structure of the peptide and some of the amino acid residues were related to the binding, we prepared a peptide-2, to which the N- and C-terminals of peptide-1 were alternated. The decrease in the response for the labeled peptide-2 was less than that for the labeled peptide-1. In addition, the peak current of a peptide-3, for which the D of peptide-1 was replaced with S, was hardly changed with or without ovalbumin. Therefore, it was clear that the binding was influenced by the steric factors and by the sequence of the peptide. However, a peptide-1 with bis(sulfosuccinimidyl) suberate was designed to investigate the hydrophobic influences on the probe. The change in the peak current was smaller than that of peptide-1 with ethylene gycolbis(sulfosuccinimidyl succinate), which was due to the hydrophobic properties of the alkyl chain between the peptide and the ovalbumin. The proposed method could be applied to the determination of ovalbumin in egg whites. Consequently, the concept becomes an electrochemical sensing method for proteins based on the protein-peptide interaction.
[Show abstract][Hide abstract] ABSTRACT: When peat forest fires happen, it leads to burn soil and also humic acids as a dominant organic matter contained in peat soil as well as the forest. The structure and properties of humic acids vary depending on their origin and environment, therefore the transformation of humic acid is also diverse. The impacts of the peat fires on peat soil from Central Kalimantan, Indonesia were investigated through the characterization of humic acids, extracted from soil in burnt and unburnt sites. The characterization of humic acids was performed by elemental composition, functional groups, molecular weight by HPSEC, pyrolysate compounds by pyrolysis-GC/MS, fluorescence spectrum by 3DEEM spectrofluorometer, and thermogravimetry. The elemental composition of each humic substance indicated that the value of H/C and O/C of humic acids from burnt sites were lower than that from unburnt sites. The molecular weight of humic acids from burnt sites was also lower than that from unburnt sites. Pyrolysate compounds of humic acids from unburnt sites differed from those of humic acids from burnt soil. The heating experiment showed that burning process caused the significant change in the properties of humic acids such as increasing the aromaticity and decreasing the molecular weight.
Environmental Science and Pollution Research 05/2014; 22(4). DOI:10.1007/s11356-014-2929-1 · 2.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To electrochemically detect concanavalin A (ConA), a new method was developed using mixed micelles between a non-ionic surfactant with a maltose moiety and electroactive daunomycin. The surfactants, in which the length of the alkyl chain was different, were n-decyl-β-d-maltoside, n-dodecyl-β-d-maltoside, and n-tetradecyl-β-d-maltoside. The measurement principle was due to the micelle breakdown caused by the binding between the ConA and maltose moieties. When ConA was combined with maltose moieties at a concentration of surfactant that was near the critical micelle concentration, the daunomycin that formed the micelles was moved to a solution from the micelles. As a result, the peak current of daunomycin increased as the concentration of ConA was increased. The mechanism was proposed using voltammetry, spectrometry, and gel filtration. The linear range using n-tetradecyl-β-d-maltoside was 2.0×10(-9) to 8.0×10(-8)M of ConA, and it was the most sensitive in the presence of the three surfactants. To examine whether selective binding took place, measurements with several proteins were carried out. The electrode responses of daunomycin were not influenced by the presence of 5.0×10(-6)M protein. Furthermore, this method could be applied to the determination of ConA in a serum, and to the measurement of sugar chains that can be combined with ConA on the cell surface.
[Show abstract][Hide abstract] ABSTRACT: Because ovalbumin was combined with lysozyme, a new method was developed to electrochemically detect ovalbumin via its binding with peptide contained in lysozyme. The measurement principle was based on the change of the electrode response caused by the binding between the peptide with an electroactive compound and ovalbumin.
[Show abstract][Hide abstract] ABSTRACT: A higher enrichment of organic pollutant, di(2-ethylhexyl) phthalate (DEHP) was found in estuary of Oyabe River and Jinzu River, Japan. Based on this, the distribution of DEHP between water and bed sediment was investigated as a model of organic pollutant through both the field investigation and laboratory experiment. The laboratory experiment was performed to examine the effect of seawater, organic matter in sediment and hydrophobicity (log K ow ) of organic pollutants. The result showed that salting-out effect due to the high salinity in seawater and organic matter in sediment contributed towards the increasing of DEHP distribution between water and sediment. Furthermore, the hydrophobicity of organic pollutant also enhances the distribution between water and sediment to a higher magnitude in the presence of seawater.
[Show abstract][Hide abstract] ABSTRACT: A micro-scale algal growth inhibition (μ-AGI) test using a common micro-plate based fluorometric detection was used to demonstrate the effects of humic substances (HSs) on the toxicity of tetrabromobisphenol A (TBBPA) and its oxidative decomposition products 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,5-dibromohydroquinone (2,5-DBHQ), 2,6-dibromobenzoquinone (2,6-DBBQ), and 2,6-dibromophenol (2,6-DBP) to Pseudokirchneriella subcapitata. The EC50 values were: EC50(TBBPA) = 7 mg L−1, EC50(2,5-DBHQ) = 7 mg L−1, EC50(2,5-DBBQ) = 19 mg L−1, EC50(2,6-DBP) = 49 mg L−1, and EC50(2,6-DBBQ) = 13 mg L−1. The toxicity of the chemicals was slightly lower in the presence of HA. The toxicity of TBBPA decomposed by a biomimetic catalytic system consisting of iron (III) 5,10,15,20-tetrakis (p-sulfonatophenyl) porphyrin (Fe(III)-TPPS) and KHSO5 was also evaluated using P. subcapitata and Chlamydomonas reinhardtii.
[Show abstract][Hide abstract] ABSTRACT: An improved molybdenum blue spectrophotometry using a soluble membrane filter and CaCO(3)-column was proposed for determining arsenic in drinking water supplied from ground water in the presence of phosphate. A 100 mL sample solution containing 0.5 - 10 μg arsenic was passed through a CaCO(3)-column to remove phosphate, arsenate (As(V)). Arsenite (As(III)) which was not retained on the column was oxidized to As(V). As(V) was converted into a heteropolymolybdenum blue anion. The blue anion was collected on a membrane filter as an ion-associate with n-dodecyltrimethylammonium ion by filtration. The filter was dissolved in 2 mL of 2-methoxyethanol. The absorbance of the solution was measured at 810 nm against a reagent blank. Total inorganic arsenic was determined by reducing As(V) to As(III) before the column treatment. The RSDs for 10 μg L(-1) of As(III) and As(V) were 2.9%. Phosphate 0.2 mg L(-1) (as P) and iron 0.1 mg L(-1) did not interfere with the determination of 10 μg L(-1) arsenic. The proposed method was successfully applied to ground waters.